Ferropericlase ormagnesiowüstite is amagnesium/ironoxide with the chemical formula(Mg,Fe)O that is interpreted to be one of the main constituents of the Earth'slower mantle together with thesilicate perovskite ((Mg,Fe)SiO3), a magnesium/ironsilicate with aperovskite structure. Ferropericlase has been found asinclusions in a few naturaldiamonds. An unusually high iron content in one suite of diamonds has been associated with an origin from the lowermost mantle.[1] Discrete ultralow-velocity zones in the deepest parts of the mantle, near the Earth's core, are thought to be blobs of ferropericlase, as seismic waves are significantly slowed as they pass through them, and ferropericlase is known to have this effect at the high pressures and temperatures found deep within the Earth's mantle.[2] In May 2018, ferropericlase was shown to be anisotropic in specific ways in the high pressures of the lower mantle, and these anisotropies may help seismologists and geologists to confirm whether those ultra-low velocity zones are indeed ferropericlase, by passing seismic waves through them from various different directions and observing the exact amount of change in the velocity of those waves.[3]
Changes in thespin state ofelectrons in iron in mantle minerals has been studied experimentally in ferropericlase. Samples are subject to the conditions of the lower mantle in alaser-heateddiamond anvil cell and the spin-state is measured usingsynchrotronX-rayspectroscopy. Results indicate that the change from a high to lowspin state in iron occurs with increasing depth over a range from 1000 km to 2200 km.[4][5]
Ferropericlase(Mg,Fe)O makes up about 20% of the volume of thelower mantle of the Earth, which makes it the second most abundant mineral phase in that region after silicateperovskite(Mg,Fe)SiO3; it also is the major host for iron in the lower mantle.[6] At the bottom of thetransition zone of the mantle, the reaction
transformsγ-olivine into a mixture of perovskite and ferropericlase andvice versa. In the literature, this mineral phase of the lower mantle is also often calledmagnesiowüstite.[7]
